The FIRM mapping system was a hot topic at the last annual AF Symposium. In his presentation Dr. Ravi Mandapati compared data from his study of FIRM ablations performed at UCLA Medical Center to the CONFIRM clinical trial data published by Dr. Sanjiv Narayan, one of the inventors of the FIRM mapping system.
Up to this point in time, everyone seemed to be jumping on the FIRM/Topera ‘bandwagon’ with very little critical analysis or understanding of how it worked.
As patients, we should now be skeptical of the FIRM system:
• It doesn’t map nearly ½ of the left atrium
• The FIRM mapping algorithms finds stable rotors that other research finds are not stable, and electrophysical characteristics that other research doesn’t confirm
• Results of ablating FIRM-identified rotor sites are relatively poor. (This is what should most concern us as patients.)
So, as an A-Fib patient, you may ask: “Should I now stay away from doctors or centers using the FIRM system?” Read my answer and my full 2015 AF Symposium report at Critical Analysis of the FIRM Mapping System.
For more background also see my 2014 AF Symposium report: ECGI vs. FIRM: Direct Comparison, Phase/Waveform Mapping.
When I think about the field of atrial fibrillation in 2013, several thoughts come to mind. There were technical advancements, some new drug therapies, and additions to our understanding of Atrial Fibrillation (and a few accomplishments for our A-Fib.com website).
Heart Imaging And Mapping Systems
Perhaps the most important technical innovations in 2013 for A-Fib patients were the introduction of two new heart imaging and mapping systems. A third system, the Bioelectronic Catheter, represents a whole new technology with tremendous potential for A-Fib patients.
The ECGI System
The ECGI system, combined with a CT scan, produces a complete 3-D image of your heart along with identifying all the A-Fib-producing spots. Think of it as an ECG with 256 special high resolution electrodes rather than 12. It greatly reduces your ablation time and your radiation exposure.
A day before your ablation, you simply don a special vest with 256 electrodes covering your upper torso, and lay down. The 3-D image created is a road map of your heart with all the focal and rotor areas (A-Fib-producing spots) identified. During your ablation your EP simply ablates the “guilty” areas. Read more of my article…
The FIRM System
The FIRM system uses a different approach to mapping the heart and the A-Fib producing spots. It uses a basket catheter inside the heart to map large areas in a single pass and reveal the location of foci and rotors. Read more of my article…
Why are these two technologies important? ECGI allows your imaging & mapping to be performed the day prior to your ablation, rather than during your ablation. This shortens the length of your ablation procedure. In addition it reduces your radiation exposure and produces remarkably accurate 3D images of your heart and identifies where A-Fib signals are coming from. The FIRM system, though performed during an ablation rather than before it, may be a significant improvement over the Lasso catheter mapping system now in current use. Both systems may mark a new level of imaging/mapping for A-Fib.
Stretchable Electronics Meets the Balloon Catheter
The merging of living systems with electronic systems is called “bioelectronics”. Key is a flexible, pliable circuit made from organic materials—the carbon-based building blocks of life. Bioelectronics have entered the EP lab with a prototype of a ‘bioelectronic catheter’, the marriage of a pliable integrated circuit with a catheter balloon.
In a mapping application, the deflated bioelectronic balloon catheter is slipped into the heart, then pumped up. The inflated integrated circuit conforms to the heart’s grooves and makes contact with hard-to-reach tissue. It can map a hundred electrical signals simultaneously, across a wider area and in far greater detail than had been previously possible. And it’s being developed to function in reverse. For ablation applications, instead of detecting current, it can apply precise electrical burns. This is a potentially breakthrough technology that may well change the way catheter mapping and ablation are performed. (Thanks to David Holzman for calling our attention to this ground-breaking research article.)
This is a remarkable time in the history of A-Fib treatment. Three very different technologies are poised to radically improve the way A-Fib is detected, mapped and ablated. We’ll look back at 2013 as a watershed year for A-Fib patients.
Three New Anticoagulants
In 2013 we saw three new anticoagulants, a welcome development for A-Fib patients. Note: the new anticoagulants are very expensive compared to the proven anticoagulant warfarin.
How do they compare to warfarin?
Warfarin seems to have a slightly higher chance of producing intracranial bleeding.
In general stay away from Pradaxa. There are horrible ER reports of patients bleeding to death from even minor cuts, because there is no antidote or reversal agent. Read more about my Pradaxa warning…
Eliquis, in general, tested better than Xarelto in the clinical trials, but it’s so new we don’t have a lot of real-world data on it yet. And, as with Pradaxa, neither have antidotes or reversal agents.
In addition, there was what some consider a major problem with the clinical trials comparing the new anticoagulants to warfarin. ‘Compliance’ rates by warfarin users were poor (many either weren’t taking their warfarin or weren’t in the proper INR range). Did this skew the results?
And finally, unlike warfarin where effectiveness can be measured with INR levels, we don’t have any way to measure how effectively the new blood thinners actually anticoagulate blood. Read more of my article “Warfarin vs. Pradaxa and the Other New Anticoagulants“.
Keep in mind: ‘New’ doesn’t necessarily mean ‘better’ or ‘more effective’ for You.
High Blood Pressure with Your A-Fib? Is Renal Denervation a solution?
As many as 30% of people with A-Fib also have high blood pressure which can’t be lowered by meds, exercise, diet, etc. There was hope that Renal Denervation would help.
With Renal Denervation, an ablation catheter is threaded into the left and right arteries leading to the kidneys, then RF energy is applied to the nerves in the vascular walls of the arteries, hopefully reducing ‘Sympathetic Tone’, lowering high blood pressure and reducing A-Fib. For many people Renal Denervation seemed the only realistic hope of lowering their high blood pressure. However, the Medtronic Simplicity-3 trial indicated that renal denervation doesn’t work. Read more of this article… For 2014 news on this topic, read more…
A Study of Obesity and A-Fib: A-Fib Potentially Reversible
Obesity is a well known cause or trigger of A-Fib, probably because it puts extra pressure and stress on the Pulmonary Vein openings where most A-Fib starts.
In 2013 A research study report focused on obese patients with A-Fib. Those who lost a significant amount of weight also had 2.5 times less A-Fib episodes and reduced their left atrial area and intra-ventricular septal thickness.
Good news! Losing weight can potentially reverse some of the remodeling effects of A-Fib. Related article: Obesity in Young Women Doubles Chances of Developing A-Fib.
Obstructive Sleep Apnea and A-Fib
Obstructive Sleep Apnea (OSA) is another well recognized cause or trigger of A-Fib. Anyone with A-Fib should be tested for sleep apnea.
Earlier studies have shown approximately two-thirds (62%) of patients with paroxysmal or persistent A-Fib suffer from sleep apnea. In 2013, research reports showed that the worse one’s sleep apnea is, the worse A-Fib can become. In addition, sleep apnea often predicts A-Fib recurrence after catheter ablation.
Before an ablation, Dr. Sidney Peykar of the Cardiac Arrhythmia Institute in Florida, requires all his A-Fib patients be tested for sleep apnea. If they have sleep apnea, they must use CPAP therapy after their ablation procedure.
A-Fib.com: Our New Website’s First Year
The original A-Fib.com web site was created using the phased out software MS FrontPage. Thanks to a “no strings attached” grant from Medtronic, A-Fib.com was reinvented with a more up-to-date but familiar look, and features more functionality (built on an infra-structure using Joomla and WordPress). We can now grow the site and add features and functions as needed.
It involved a tremendous amount of work. A special thanks to Sharion Cox for building the new site and for technical support. My wife, Patti Ryan, designed the look and all graphics. (I can’t thank Patti enough; I’m so lucky!)
Update the Directory of Doctors & Facilities
Back when I started A-Fib.com in 2002, there were less than a dozen sites performing ablations for A-Fib. Today our Directory of Doctors and Facilities lists well over 1,000 centers in the US, plus many sites worldwide.
Increasingly, doctors were writing me asking why they weren’t included, or why their info was incorrect since they had moved, etc. To update our records and our service to A-Fib patients, starting in July 2013, we prepared and mailed letters to over 1,000 doctors/facilities. We asked each to update/verify their listing (and include a contact person for our use).
The response to our bulk mailing was great. The data input started in October and continued for several months (as time allowed). Recently, we cut over to the ‘new’ Directory menu and pages.
What’s Ahead for A-Fib.com in 2014
2014 Boston AFib Symposium Reports: Check out my new reports from the 2014 Boston A-Fib Symposium (BAFS) held January 9-11, 2014 in Orlando FL.
The first two reports are posted. Look for more reports soon. I usually end up with 12-15 reports in total.
Our a-Fib.com Directory of Doctors & Facilities: Work on updating our listings is still underway. We need to contact those who did not respond to our request for verification or updating of their listing. (Shall we write again or maybe make phone calls?)
Amazon Best Sellers list: Our book sales continue to grow. Did you know that our book ‘Beat Your A-Fib’ has been on Amazon’s Best Sellers list continually in two categories (Disorders & Diseases Reference and Heart Disease) since its debut in March 2012? Visit Amazon.com and read over 40 customer reviews.
Help A-Fib.com Become Self-sustaining: We plan to step up our efforts to make A-Fib.com a self-sustaining site. (Since 2002, Steve and Patti Ryan have personally funded A-Fib.com with an occassional reader’s donation.)
In our efforts toward sustainabiliy, several years ago we added a PayPal ‘Donate’ button (you don’t need a PayPal account to donate) and invited donations toward our onlline maintenance costs.
Our newest effort is our ‘A-Fib can be Cured! shop with T-shirts and more at Spreadshirt.com. With each shirt purchase $2 goes to support A-Fib.com. (We will roll out new designs every quarter or so).
Posted February 2014
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Last updated: Wednesday, February 11, 2015
ECGI vs. FIRM: Direct Comparison, Phase/Waveform Mapping
Report by Dr. Steve S. Ryan, PhD
In a further discussion of the ECGI mapping and ablation system, Dr. Phillip Cuculich of the Washington University School of Medicine in St. Louis, MO gave a presentation entitled “Advances in and Limitations of Noninvasive Mapping of AF.” (For a detailed description and discussion of the ECGI system, see 2013 BAFS: Non-Invasive Electrocardiographic Imaging ECG (ECG).
Background: ECGI stands for Non-Invasive Electrocardiographic Imaging used at Yoram Rudy’s lab at Washington University in St. Louis to understand the mechanisms of heart rhythm disease. A similar system called Electrocardiographic Mapping (ECM/ecVUE) uses similar technology, but has been developed and tested for clinical use in Europe (http://www.cardioinsight.com) and has different goals. Each group works independently and has different ways to seek solutions.
The software used by the ECGI system to produce data and images from the multi-channel ECG mapping and CT scan is called CADIS.
POTENTIAL BENEFITS OF ECGI
Dr. Cuculich began by describing the potential benefits of ECGI:
• Save time: Locate the arrhythmia in a single beat
• Better Preparation: Understand and plan for the arrhythmia before an ablation
• Avoid Frustration: Map and ablate unstable, transient or complex arrhythmias
• Research Platform for Discovery: Identify and describe the mechanisms of arrhythmias
A-FIB PATTERNS OR SIGNALS AS REVEALED BY ECGI
After imaging patients with ECGI, A-Fib patterns are a combination of mechanisms:
• In simple A-Fib, Dr. Cuculich showed movies of left pulmonary vein focal sites with 1 to 2 wavelets and a left-to-right activation pattern
• In complex (Long-standing Persistent) A-Fib, he showed movies of four or more simultaneous wavelets, a high degree of wavelet curvature, and frequent wave breaks (no focal sites). The patterns tend to repeat and follow a preferred path.
FIRM AND ECGI COMPARISON
|Inside the heart||Outside the heart (body surface mapping)|
|Up to 64 contact electrodes to produce up to 64 electrograms||1000 reconstructed electrodes|
|QRST subtracted||No signal subtraction|
|70% rotor, 30% focal||Multiple wave fronts (1-4), 15% rotor|
|Stable beat-to-beat||Transient focal activity, transient rotational circuits|
(In the ECGI imaging/mapping system the number of points on the heart is changeable. But they have found 1000 to be a good number for reliable, detailed analysis.)
Dr. Cuculich compared ECGI data to recent invasive epicardial (inside-the-heart) mapping and body surface mapping (called “Phase Lock”). The data showed significant agreement between the imaging systems. Also, ECGI compares favorably to surgical maze mapping data.1
But compared to FIRM, the most common patterns of A-Fib Dr. Cuculich found were multiple wavelets, with pulmonary vein and non-pulmonary vein focal sites. Rotor activity was seen rarely.2
NO STANDARD DEFINITION OF “ROTOR”
There is no standard definition of a rotor. In Dr. Cuculich’s studies he used 2 rotations at the same spot as a “rotor.” This is perhaps why he found less rotors than in the FIRM system and in the CardioInsight system as described by Dr. Jais where they found 80% rotors. See: BAFS 2014 Jais, ECGi & Circular Catheter
Another major difference in ECGI and FIRM is that ECGI uses wavelet analysis (activation of the wavefront), while FIRM and CardioInsight uses phase mapping to describe the behavior of the arrhythmia. The main point of Dr. Cuculich’s presentation is that one must be very careful when applying phase techniques, as it can introduce rotor behavior into the imaging map. Dr. Cuculich’s group is studying whether this rotor behavior may be a true cause for the maintenance of A-Fib or just an artifact.
ECGI—TOO MANY ELECTRODES?
In a conversation with the author, Dr. Cuculich brought up comments that perhaps ECGI/ECM uses too many electrodes to see stable rotors, that perhaps panoramic imaging with fewer electrodes could improve the identification of rotors. (ECGI has a much larger number of electrode points in the heart [usually 1000] compared to FIRM [64 max].) To test this hypothesis, he analyzed A-Fib using 64 spaced electrodes in each atrium vs. standard ECGI. It turned out that fewer electrodes did not help to visualize rotors.
PHASE MAPPING, WAVEFRONTS, WAVELET TRANSFORMATION, ACTIVATION PATTERNS
Dr. Cuculich introduced new concepts in the use of ECGI (at least to this author)—phase mapping and the importance of wavefronts or wavelet transformation in A-Fib signals. “ECGI uses wavelet transform looking at pure activation time.” He asked, “how does…phase mapping affect the result?” He related phase mapping to the CONFIRM concept of “phase lock” where a simple 12-lead ECG analysis can classify A-Fib mechanistically.3
Doctors (and we patients) are still struggling to understand what phase mapping and wavelet transformation actually mean. Dr. Cuculich’s studies of phase mapping techniques (Hilbert transform) in A-Fib show that phase mapping highlights and accentuates the curvature of a wavefront and thus indicates a rotor is present. According to Dr. Cuculich, phase mapping is highly dependent on the chosen cycle length. He concluded that “while published ECGI data used wavelet transform to identify activation patterns, phase mapping techniques (when performed carefully and correctly) may offer additive information.”
We’re grateful to Dr. Cuculich for his comparison of ECGI and FIRM which helps us understand both imaging system better. But it’s definitely disturbing that both systems vary so greatly. Why does the FIRM system find 70% rotors and ECGI only 15%? Why are FIRM’s A-Fib signals stable and ECGI’s transient? Why does the FIRM system not focus on wavefronts and wavelet transformation?
One way to resolve these discrepancies would be to use a standard Lasso mapping catheter to meticulously map every potential A-Fib-producing spot in an animal or human with Long-standing Persistent A-Fib (where one would expect to find multiple A-Fib producing spots in the heart). Then immediately use both the FIRM and ECGI system to map the same heart and compare the results.
Perhaps the single biggest new discovery in human A-Fib mapping is rotors. But there’s considerable debate about their definition and behavior. Dr. Cuculich found that rotors are relatively rare (15%), whereas the FIRM and CardioInsight studies indicate that 70-80% of A-Fib drivers are rotors.
Dr, Cuculich introduced new concepts, insights and vocabulary to our understanding of A-Fib, (some of which I’m still having trouble wrapping my head around). Are wavefronts and wavelet transformation important in themselves or are they part of the development of rotors? Phase mapping and wavelet transformation applied to A-Fib is a major innovation that may lead to a better understanding of how A-Fib signals activate in the heart. Besides making mapping and ablating A-Fib easier and more effective, ECGI with its detailed, high resolution capabilities may give us new insights into A-Fib.
- Lee, G. et al. Epicardial wave mapping in human long-lasting persistent atrial fibrillation: transient rotational circuits, complex wavefronts, and disorganized activity. European Heart Journal (2104) 35, 86-97. Last accessed May 13, 2013, URL:http://www.ncbi.nlm.nih.gov/pubmed/23935092 doi:10.1093/eurheartj/eht267↵
- Cuculich, PS et al. Noninvasive characterization of epicardial activation in humans with diverse atrial fibrillation patterns. Circulation. 2010 Oct 5; 122(14): 1365-72. Last accessed May 13, 2013, URL: http://tinyurl.com/okp4229↵
- Non-invasive identification of stable rotors and focal sources for human atrial fibrillation: mechanistic classification of atrial fibrillation from the electrocardiogram, Europace. February 28, 2013. Last accessed May 13, 2013, URL: http://tinyurl.com/njt9zd7; doi:10.1093/europace/eut038↵